✅ Collection appears to be null, even though it's not null on DB

KooriByte · 2023-02-05T19:47:05.719Z

I think the pictures already show the problem in more detail, there isn't much to it. User and Person have a many to many relationship, and that is all, I think... I don't have the slightest clue on why it says this. Would appreciate some help on this, tkss 😄

K

KooriByteOP•2/5/23, 7:49 PM

The issue here is that I can't test if this user is already related to this person

K

KooriByteOP•2/5/23, 7:49 PM

originally it was just user.People.Add(person), but at some point I added those person lines too for some reason

D

djmurp•2/5/23, 7:56 PM

yes, .Include(x => x.People) in the code inside GetUserAsync.

This is so that EF only gets from the DB what you ask for (otherwise it would write very inefficient SQL even if you only wanted a single field)

K

KooriByteOP•2/5/23, 7:58 PM

oh, that is what he meant, I did not understand when he answered

K

KooriByteOP•2/5/23, 7:58 PM

thank you a lot, will try it now

K

KooriByteOP•2/5/23, 8:00 PM

I might be doing something wrong again

K

KooriByteOP•2/5/23, 8:00 PM

is is suposed to be like this:

var user = _userManager.GetUserAsync(User.Include(x => x.People)).Result;

var user = _userManager.GetUserAsync(User.Include(x => x.People)).Result;

var user = _userManager.GetUserAsync(User.Include(x => x.People)).Result;

var user = _userManager.GetUserAsync(User.Include(x => x.People)).Result;

?

K

KooriByteOP•2/5/23, 8:01 PM

forgot to correct

K

KooriByteOP•2/5/23, 8:01 PM

ops

K

KooriByteOP•2/5/23, 8:01 PM

in discord

D

djmurp•2/5/23, 8:01 PM

do you own the method "GetUserAsync"? (can you edit it)

Ddjmurp do you own the method "GetUserAsync"? (can you edit it)

K

KooriByteOP•2/5/23, 8:02 PM

nop, it is from Identity

K

KooriByteOP•2/5/23, 8:04 PM

this is the only User property that VS says is null

K

KooriByteOP•2/5/23, 8:04 PM

the rest of them are showing just fine (name, email, etc)

D

djmurp•2/5/23, 8:04 PM

unfortunately you can't .Include the navigation property called .People then. So you will have to get the user from the _context itself

D

djmurp•2/5/23, 8:05 PM

some properties are fine because they are columns in the same user table, but it won't go and get related entities from a different table (like .People)

K

KooriByteOP•2/5/23, 8:06 PM

I think I already done this, here

  public async Task<IActionResult> Details(int? id)
        {
            if (id == null || _context.People == null)
            {
                return NotFound();
            }

            var person = await _context.People
                .Include(x => x.ApplicationUsers)                
                .FirstOrDefaultAsync(m => m.Id == id);
            if (person == null)
            {
                return NotFound();
            }

            return View(person);
        }

  public async Task<IActionResult> Details(int? id)
        {
            if (id == null || _context.People == null)
            {
                return NotFound();
            }

            var person = await _context.People
                .Include(x => x.ApplicationUsers)                
                .FirstOrDefaultAsync(m => m.Id == id);
            if (person == null)
            {
                return NotFound();
            }

            return View(person);
        }

  public async Task<IActionResult> Details(int? id)
        {
            if (id == null || _context.People == null)
            {
                return NotFound();
            }

            var person = await _context.People
                .Include(x => x.ApplicationUsers)                
                .FirstOrDefaultAsync(m => m.Id == id);
            if (person == null)
            {
                return NotFound();
            }

            return View(person);
        }

  public async Task<IActionResult> Details(int? id)
        {
            if (id == null || _context.People == null)
            {
                return NotFound();
            }

            var person = await _context.People
                .Include(x => x.ApplicationUsers)                
                .FirstOrDefaultAsync(m => m.Id == id);
            if (person == null)
            {
                return NotFound();
            }

            return View(person);
        }

K

KooriByteOP•2/5/23, 8:06 PM

OOH

K

KooriByteOP•2/5/23, 8:06 PM

i think I understood it know

K

KooriByteOP•2/5/23, 8:08 PM

nah, I didn't :/

D

djmurp•2/5/23, 8:09 PM

yep you've done the same thing, it's just that unfortunately you can't .Include that property when calling the built in Identity method - I thought you owned that code but you didn't

D

djmurp•2/5/23, 8:11 PM

do you know what table your users are in?

K

KooriByteOP•2/5/23, 8:12 PM

in my db?

D

djmurp•2/5/23, 8:13 PM

yeh, or the equivalent property name in your context

K

KooriByteOP•2/5/23, 8:15 PM

users are in an ApplicationUser table, all "persons" are in a People table, and there is an intermediary table ApplicationUsersPeople between this two that have both the ApplicationUserId and PersonId

K

KooriByteOP•2/5/23, 8:16 PM

for the many to many relationship

K

KooriByteOP•2/5/23, 8:16 PM

I think that was the answer to your question, I'm not sure if I answered correctly, sorry :/

D

djmurp•2/5/23, 8:17 PM

then you will have to query

var userWithPeople = _context.ApplicationUsers.Include(x => x.People).FirstOrDefault(x => x.Id == user.Id);

var userWithPeople = _context.ApplicationUsers.Include(x => x.People).FirstOrDefault(x => x.Id == user.Id);

var userWithPeople = _context.ApplicationUsers.Include(x => x.People).FirstOrDefault(x => x.Id == user.Id);

var userWithPeople = _context.ApplicationUsers.Include(x => x.People).FirstOrDefault(x => x.Id == user.Id);

or similar after the userManager.GetUserAsync(User) call

K

KooriByteOP•2/5/23, 8:20 PM

and then I change user in the code bellow for userWithPeople afterwards?

K

KooriByteOP•2/5/23, 8:20 PM

will try it, just a minute

D

djmurp•2/5/23, 8:21 PM

yes that should work in a readable way

D

djmurp•2/5/23, 8:22 PM

I have another code recommendation but we can solve this first

K

KooriByteOP•2/5/23, 8:22 PM

it said that the ApplicationUsers after _context was null

K

KooriByteOP•2/5/23, 8:24 PM

I'll change it for _userManager, just a sec

edit: this was just wrong

D

djmurp•2/5/23, 8:24 PM

check this https://stackoverflow.com/questions/39837355/eager-loading-using-usermanager-with-ef-core, the answer for you actually in the question itself

K

KooriByteOP•2/5/23, 8:25 PM

oh, thank you, I'll read it

K

KooriByteOP•2/5/23, 9:19 PM

do you know if there is another approach for this? I still couldn't make it work

D

djmurp•2/5/23, 9:24 PM

another approach would be entity framework lazy loading (in that case accessing .People will trigger additional SQL) but i'd avoid if possible - it's convenient but much less efficient!

D

djmurp•2/5/23, 9:25 PM

you can investigate it to see if it suits your use case, but feel free to persist and post an update instead

J

jcotton42•2/5/23, 9:32 PM

you really do not want to use lazy loading in EF

J

jcotton42•2/5/23, 9:32 PM

surprise, synchronous, network IO on a property access is a nasty surprise

K

KooriByteOP•2/5/23, 9:37 PM

noooo, was half way into it already

K

KooriByteOP•2/5/23, 9:37 PM

well, I think I'll try another solution

K

KooriByteOP•2/5/23, 9:38 PM

this is way out of my current knowledge level, it's really frustrating sometimes

K

KooriByteOP•2/5/23, 9:45 PM

is there a reason why only People is not working here?

J

jcotton42•2/5/23, 9:50 PM

oh, is this asp.net identity?

K

KooriByteOP•2/5/23, 9:53 PM

yep

J

jcotton42•2/5/23, 9:53 PM

you might want to ask in #web or #database then

J

jcotton42•2/5/23, 9:53 PM

this might also help https://learn.microsoft.com/en-us/ef/core/querying/related-data/explicit

Explicit Loading of Related Data - EF Core

Explicit loading of related data with Entity Framework Core

D

djmurp•2/5/23, 9:54 PM

it's empty because you are going via userManager, something provided to you via Identity.

It doesn't automatically know that you want all related data so it gives you the basics (column values). Anything more would result in a lot of SQL JOINs

✅ Collection appears to be null, even though it's not null on DB

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